...work can lead to stress in many cases. In the book, “The Andromeda Strain”, by Michael Crichton, four scientists try to find the source of the destruction caused in Piedmont. Discovering how all the inhabitants in the town of Piedmont died, except for two, was a stressful process that was worked on by the group of scientists. They were to look for the answer through clues and discoveries. Two scientists look around Piedmont with no ideas on where to begin looking for clues. They entered Piedmont worried about the amount of work to be done, “They were painfully aware of how much there was to learn, to do. Some catastrophe had struck this town, and they must discover all they could about it. But they had practically no clues, no points of departure” (Crichton 85-86). It was very stressful arriving into Piedmont, especially when they had “no clues”. They were to find many factors in the town that would contribute to finding a prevention, so the endangerment of other people was in their hands. Stress from events like these may cause or foreshadow anger....
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...bar in tension, and 2) an aluminum bar in tension. The specific types of materials used in this experiment are grade 50 for the steel, and type 2017-T351 for the aluminum. The experimental procedure and analysis give a better insight to the behavior of different ductile materials under normal stresses. Through the analysis of the experimental data, various properties of the material can be found and these properties are used in the design of engineering structures which use these materials. Through the use of plots of the stress versus strain for each material, and tables providing material properties, the report will include the following objectives for all materials: • Describe the behavior in the elastic range by determining the moduli of elasticity, and yielding stresses. • Describe the behavior of the materials beyond yielding by determining plastic stresses, ultimate stresses, rupture stresses, and ductility as well as indicating the range of strain hardening and necking. • Compare computed values obtained from the test results to expected values found for steel and aluminum. Further, the report will assist in obtaining the objectives stated above by giving and organized presentation of the experimental and analysis procedure, and conclusions of the experiment. Procedure Experimental In this set of laboratory experiments, uniaxial tests were performed on two specimens: 1) a steel bar in tension, and 2) an aluminum bar in tension. The procedure of the...
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... Abstract: We determined the elastic modulus, yield strength, tensile strength, modulus of toughens, elongation, reduction of area, as well as true stress and strain at rupture point for one specimen, aluminum,. We accomplished this by placing our specimen at a time into a universal testing machine (UTM), which, under computer control, slowly increased the tension force on each specimen, stretching each until failure. Purpose: The purpose of this experiment is to extract data on the material properties one specimen (aluminum), using a mechanically driven universal testing machine (UTM). The material properties include the following: the elastic modulus, 0.2% offset yield strength, ultimate tensile strength, modulus of rupture, modulus of resilience, as well as true strain and true stress at the point of rupture. Theory: Certain materials (those that are linear, homogeneous, elastic, and isotropic) can be described by their material properties. These properties include the modulus of elasticity, modulus of toughness, modulus of resilience, ultimate tensile strength, and yield strength. Once established by experimental means, these properties are then applied to all instances of that material undergoing the same type of stress, allowing one to design structural elements whose behavior can be predicted. In practice, these qualities are affected by temperature and repeated loading, and also by the purity of the material-...
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...after deformation. stress – characterizes the strength of forces causing the deformation. F stress A in 2 or pascal (Pa) strain – the resulting deformation. Hooke’s Law: stress elastic mod ulus strain 3 Types of Stress tensile or compressive stress – changes the length of a strained body. tensile stress bulk stress – changes the volume of a strained body. bulk stress shear stress – opposite forces act at different points in the body. shear stress Tensile and Compressive Stress Consider a body of initial length lo acted upon by a tensile or compressive force of F. F stress A l strain lo Young’s Modulus (Y) F stress A Y strain l l o Flo Y Al Example 1 Bulk Stress When uniform pressure p acts on a body, the volume of the body decreases. F pressure stress A V strain Vo F stress A B strain V V o Bulk Modulus (B) p B V V o B p V Vo Example 2 Shear Stress and Strain When equal and opposite forces act tangent to the opposite sides of a body, a shear strain is produced. F// stress A x strain h x h x tan h Shear Modulus (S) F// h S Ax F// S A tan Example 3 F// = 9.0 x 105 N A = 5.0 x 1-4 m2 F Ssteel = 7.5 x 1010 Pa a ) s. strain s. stress F// 2.4 x10 2 ...
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..........................................................6 7. Conclusion…...................................................................................................9 8. References ....................................................................................................9 Summary: Tensile testing is one of the simplest and most widely used mechanical tests. By measuring the force required to elongate a specimen to breaking point, material properties can be determined that will allow designers and quality managers to predict how materials and products will behave in their intended applications. The test provides information on proof stress, yield point, tensile strength, elongation and reduction of area. To test miniature specimens subjected to tensile loading at room temperature, and at a constant strain rate Tensile testing is one of the simplest and most widely used mechanical tests....
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...analysis of plane stress. Since their walls offer litter resistance to bending, it may be assumed that the internal forces exerted on a given portion of wall are tangent to the surface of the vessel. The resulting stresses on an element of the wall will thus be contained in a plane tangent to the surface of the vessel. In this experiment, we are going to determine the circumferential stress under open condition, and analysis of combined axial and circumferential stress. We propose to determine the stresses exerted on a small element of wall with sides respectively parallel and perpendicular to the axis of the cylinder. Because of axis symmetry of the vessel and its contents, it is clear that no shearing stress is exerted on the element. It can be seen that all strains are used to calculate stress. As it is not possible to measure all strains, these have to be computed on the basis of marginal conditions. With this experiment it is not possible to measure in particular longitudinal strain in the body and radian strain perpendicular to the surface. Initial stress at the surface must be zero, longitudinal stress is constant over the radius are the marginal conditions to obtain the solution. The average E value we obtain from graph was 64 GN/m2. with the help of the computer, the Poisson’s ratio, v =0.35 and the principal strains for the thin cylinder were also calculated using formulas and the Mohr’s circle. For open ends conditions. The lower principal strains, εL1 = -191 με, which...
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...Calculations 10 VI. Discussion and Conclusions 11 VII. Reference 13 Appendices Appendix A. Drawings of Equipment 14 Appendix B. Experimental Data 16 Appendix C. Picture of the failure 17 List of Tables Table 1. Dimensions of the Specimen Table 2. Stress and Strain Table 3. Theoretical Strain Table 4. Offset Strain Table 5. Tensile Properties Table 6. Experimental Data List of Figures Figure 1. Plot of Experimental and Theoretical Data Figure 2. Graph for Elastic Region Figure 3. 0.1% and 0.5% Offset Intersection Figure 4. 0.1% and 0.5% Offset Intersection at 100psi Interval Scale Figure 5. Failure of the Specimen I. Objective The objective of the experiment was to test a sample specimen for various physical properties such as yield stress and ultimate tensile stress. The sample specimen was mounted on the Tinius Olsen Tension and Compression Machine with 120,000lbs capacity located in the Structural Analysis Lab (room LL210). Then the specimen was subjected to a tensile load until failure. By analyzing the type of failure and elongation of the specimen under continuously increasing load, the mechanical properties of the specimen could be verified. Furthermore, the relationship between stress and strain could be confirmed by the experiment. II. Experiment The sample aluminum bar specimen (2024-T351) was mounted on Tinius Olsen Tension...
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...Stress-Strain Equipment | Included: | | 1 | Stress-Strain Apparatus | AP-8214A | 1 | Force Sensor | PS-2104 | 1 | Rotary Motion Sensor | PS-2120 | 1 | Calipers | SF-8711 | | Required but Not Included: | | 1 | 850 Universal Interface | UI-5000 | 1 | PASCO Capstone Software | UI-5400 | Introduction The objective of this lab is to find the relationship between tensile stress and strain for various materials. The Stress-Strain Apparatus stretches (and in some cases breaks) a test coupon while it measures the amount of stretch and force experienced by the test coupon. Software is used to generate a plot of stress versus strain, which allows Young's Modulus, the elastic region, the plastic region, the yield point, and the break point to be ascertained. Theory The ratio of the force (F) applied to the cross-sectional area (A) of a material is called the stress: Stress=FA (1) The ratio of the change in length (L) to the original length (Lo) of a material is called the strain: Strain=∆LLo (2) Stress (Pa) Strain Elastic Region Plastic Region Yield Point Stress (Pa) Strain Elastic Region Plastic Region Yield Point In the elastic region, the stress is proportional to the strain and the proportionality constant is called Young’s Modulus, Y. Y=StressStrain (3) Set-Up Figure 1. Stress/Strain Apparatus Assembly 1. Open the PASCO Capstone software on the computer. 2. Connect the Stress/Strain apparatus to the computer...
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...Tension Test [pic] (Fractured Copper Specimen) By: Christl Burns Mechanics of Materials Sec. 4 Lab Preformed on: 2/9/12 Introduction The tensile test was preformed on the following commonly used materials; 836 Cold Rolled Steel, T351-2024 Aluminum, 110 Copper, Grey Cast Iron, and HDPE Plastic. The first objective was to examine the stress-strain curves in order to calculate and identify the significant mechanical properties of these materials. The curves are also used to give a better understanding of what these mechanical properties mean. The second objective was to compare the mechanical properties and physical appearance of these materials. In order to get the stress-strain curves, each specimen was placed in the tensile testing apparatus. The load frame slowly stretches the specimen until it breaks. The extensometer, was placed directly on the specimen and was hooked up to a computer program that collected all of the data, which was used to make the stress-strain curves. Procedure First a punch was used to mark off a two inch section on each specimen. This section was marked off so that it could be used as a reference in finding the elongation of the specimen.Then, using a caliper, the diameter of each was measured and recorded. Now the mechanist calipers were set up in increments of 0.05 inches starting at 2.05 inches. Next the specimen was loaded into the tensile testing apparatus, the extensometer was put onto the specimen, and the data-acquisition...
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...by means of a torsion test machine. This machine consisted of two drill chucks: one was attached to a rotating chain-driven wheel, and the other was held stationary. A potentiometer was used to determine the number of revolutions the rotating wheel had undergone. Strain gauges were attached to the stationary drill chuck. LabVIEW was used to measure and record the data from the potentiometer as well as the strain gauges. Each sample was measured until it failed. The length of each specimen as well as the diameter was recorded in order to perform calculations. Also, the diameter of the potentiometer as well as the drill chuck, as well as the minimum and maximum resistance of the potentiometer was recorded for calculations. Results/Discussion The recorded measurements are shown in the table below. These were necessary to perform the calculations. Rmin Potentiometer | 1.4212 ohms | | Rmax Potentiometer | 1985.2 ohms | | DChuck | 2.045" | | Dpotentiometer | 1" | | | Aluminum | Brass | Length | 4.85" | 5.04" | Diameter | 0.379" | 0.374" | Table 1 – Recorded Values Data was provided relating the torque to the twisting moment. The units of torque were converted into Nm from lb-in and the strain values...
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...Figure 2: Stress- strain graph The stress strain relation dependent on time and time-depending behavior of materials is known as visco-elasticity. This term derived in two expressions: Viscosity and Elasticity, Elasticity is about solid whereas Viscosity resistance to flow in fluids. Therefore, this type of material is a combination of fluid and solid properties which presents a following relation (1) where is stress tensor, is visco-elastic coefficient and is strain rate. In my thesis research problems we have choose Kelvin Voigt model. Since Kelvin gives Voigt model for visco-elastic solids. This...
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...load applied over short interval) * Dead load- Static load, always applied (weight of the structure) * Live load- Dynamic loads, (people in a building or movable objects) * Stress-Strain Relations * Stress : σ=FA (psi, ksi, kPa, MPa, GPa) * Strain: ε=Change in LengthOriginal Length (%, in/in, mm/mm) * Elastic behavior * Elasticity- instantaneous response (deformation to load) and must return to its original shape when the load is removed. Stretches the bonds between atoms-doesn’t change arrangement of atoms * Young’s Modulus (Modulus of Elasticity)- Slope of the linear portion of the stress-strain curve E=σε * Poisson’s ratio- Ratio of the lateral strain to the axial strain (must be between 0.0(compressible material)-0.5(does not change volume when load applied)) Usually between 0.1 and 0.45 ν=-εlεa * Generalized Hooke’s Law * εx=σx-ν(σy+σz)E * εy=σy-ν(σz+σx)E * εz=σz-ν(σx+σy)E * Tangent Modulus- the slope of the tangent at a point on the stress-strain curve * Chord Modulus- the slope of a chord drawn between two points on the stress- strain curve * Initial Tangent Modulus- the slope of the tangent of the stress-strain curve * Secant Modulus- the slope of a chord...
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...analysis of plane stress. Since their walls offer litter resistance to bending, it may be assumed that the internal forces exerted on a given portion of wall are tangent to the surface of the vessel. The resulting stresses on an element of the wall will thus be contained in a plane tangent to the surface of the vessel. In this experiment, we are going to determine the circumferential stress under open condition, and analysis of combined axial and circumferential stress. We propose to determine the stresses exerted on a small element of wall with sides respectively parallel and perpendicular to the axis of the cylinder. Because of axis symmetry of the vessel and its contents, it is clear that no shearing stress is exerted on the element. It can be seen that all strains are used to calculate stress. As it is not possible to measure all strains, these have to be computed on the basis of marginal conditions. With this experiment it is not possible to measure in particular longitudinal strain in the body and radian strain perpendicular to the surface. Initial stress at the surface must be zero, longitudinal stress is constant over the radius are the marginal conditions to obtain the solution. The average E value we obtain from graph was 64 GN/m2. with the help of the computer, the Poisson’s ratio, v =0.35 and the principal strains for the thin cylinder were also calculated using formulas and the Mohr’s circle. For open ends conditions. The lower principal strains, εL1 = -191 με, which...
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...613-951-4598 or perspectives@statcan.ca. Work stress and job performance Jungwee Park W ork stress is defined as the harmful physical and emotional responses that occur when job requirements do not match the worker’s capabilities, resources, and needs (National Institute of Occupational Safety and Health 1999). It is recognized world-wide as a major challenge to individual mental and physical health, and organizational health (ILO 1986). Stressed workers are also more likely to be unhealthy, poorly motivated, less productive and less safe at work. And their organizations are less likely to succeed in a competitive market. By some estimates work-related stress costs the national economy a stag-gering amount in sick pay, lost productivity, health care and litigation costs (Palmer et al. 2004). Work stress can come from a variety of sources and affect people in different ways. Although the link between psycho-social aspects of the job and the health and well-being of workers has been well documented (Dollard and Metzer 1999), limited work has been done on the effects of distinct stressors on job per-formance. As well, various protective factors can pre-vent or reduce the effects of work stress, and little research has been done toward understanding these mitigating individual and organizational factors. One important source of work stress is job strain. According to the demand/control model (Karasek 1979), job strain is determined by the interactions between...
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...Work stress and job performance Jungwee Park W ork stress is defined as the harmful physical and emotional responses that occur when job requirements do not match the worker’s capabilities, resources, and needs (National Institute of Occupational Safety and Health 1999). It is recognized world-wide as a major challenge to individual mental and physical health, and organizational health (ILO 1986). Stressed workers are also more likely to be unhealthy, poorly motivated, less productive and less safe at work. And their organizations are less likely to succeed in a competitive market. By some estimates work-related stress costs the national economy a staggering amount in sick pay, lost productivity, health care and litigation costs (Palmer et al. 2004). Work stress can come from a variety of sources and affect people in different ways. Although the link between psycho-social aspects of the job and the health and well-being of workers has been well documented (Dollard and Metzer 1999), limited work has been done on the effects of distinct stressors on job performance. As well, various protective factors can prevent or reduce the effects of work stress, and little research has been done toward understanding these mitigating individual and organizational factors. One important source of work stress is job strain. According to the demand/control model (Karasek 1979), job strain is determined by the interactions between psychological demands and decision latitude (see Work stress)...
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