Design Guide - Solvay Plastics

More documents

Recommendations

Info

Stress, MPa Figure 70: Tensile Creep Rupture, Amodel A-1133 HS Resin 200 150 100 50 65°C (149°F) 100°C (212°F) 150°C (302°F) 0 0 0.01 0.1 1 10 100 1,000 10,000 Time to Rupture, Hours If the application requires that the load be sustained for a long time, we would expect the deflection to be greater than this because of creep. To calculate the deflection considering the creep, we would use the apparent modulus instead of the short-term flexural modulus. The value of apparent modulus shown for Amodel A-1133 HS resin at 1000 hours in Figure 70 is 7.58 GPa (1.10 Mpsi). Therefore the calculated deflection is: Y= (10 kg × 9.8066)(.1m) 3 3(7.58 × 10 9 Pa)(4.5 × 10 -10 m 4 ) 25 20 15 10 5 Stress, kpsi Calculating Allowable Stress - Creep Rupture If a load is sustained for a long time and if the load and/ or temperature are high enough, rupture of the part will eventually occur due to creep. To estimate the combinations of time, temperature, and load that will cause this type of failure, creep rupture tests are conducted at various temperatures as shown in Figure 70. This figure illustrates the actual time to failure for different levels of stress so that a creep rupture envelope can be obtained. From this envelope, the safety factor in time or stress can be determined for that particular temperature. For instance, if the application life is 1,000 hours at 65°C (149°F) for a part molded from Amodel A-1133 HS resin, the curve indicates that rupture will occur within that time frame if the part is exposed to a stress level of approximately 158 MPa (23 kpsi). If the part can be redesigned to reduce the stress to 124 MPa (18 kpsi), the predicted time to rupture is now well beyond 10,000 hours. This automatically builds a safety factor into the design. Actual part testing is still recommended to confirm these results. For operating temperatures that are different from the tested temperatures, information is usually extrapolated from known creep rupture envelopes to approximate the envelope for the temperature of interest. Y= 9.6 mm (0.38 in) The deflection is about 50% greater when a sustained load is considered. 70 Amodel ® PPA Design Guide www.SolvaySpecialtyPolymers.com
Considering Stress Concentrations Classical mechanical design may result in a component design which fails prematurely or at a much lower stress than predicted. This could arise due to stress concentration. Stress concentrations may occur at sharp corners, around holes, or other part features. Impact and fatigue situations are especially sensitive to stress concentrations. Minimizing sharp corners reduces stress concentrations and results in parts with greater structural strength. To avoid stress concentration problems, inside corner radii should be equal to at least half of the nominal wall thickness. A fillet radius of 0.4 mm (0.015 in.) should be considered minimum. Figure 71 shows the effect of inside corner radius on the stress concentration factor. For example, if the nominal wall thickness is 2 mm (0.080 in.) and an inside corner radius is 0.5 mm (0.020 in.), then the radius to thickness ratio is 0.25 and the stress concentration factor will be over two. A stress of x will have the effect of over 2x on the part. Outside corners should have a radius equal to the sum of the radius of the inside corner and the wall thickness to maintain a uniform wall thickness. Figure 71: Stress Concentration Factor at Inside Corners Considering Thermal Stresses When a plastic part attached to metal undergoes temperature changes, stresses may be induced that should be considered by the designer in the development of the part design. Figure 72 illustrates a typical plastic flange fastened by a steel bolt to a steel frame. Because the thermal expansion of the plastic is significantly greater than that of the steel, an increase in temperature will produce an increase in compressive stresses in the plastic and tension in the bolt. It is the increase in compressive stress under the washer that must be considered if creep and loss of torque load on the bolt is of concern. For example, the change in length of a material when exposed to a change in temperature is given by: where ΔL = L (T F − T O )α ΔL = change in length L = original length α = coefficient of thermal expansion T F = final temperature T O = original temperature Figure 72: Thermal Stress Example Stress Concentration Factor 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 Washer Plastic Steel Bolt L 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Radius/Thickness Ratio Steel Design Information Amodel ® PPA Design Guide 71
Page 1:
Amodel® Amodel ® PPA Design Guide
Page 4 and 5:
Electrical Properties. ............
Page 6 and 7:
List of Figures Figure 1: Modulus C
Page 9 and 10:
Introduction Amodel ® Polyphthalam
Page 11 and 12:
Moisture Effects Like other polymer
Page 13 and 14:
Nomenclature Amodel ® PPA grade no
Page 15 and 16:
Table 4: Glass-Reinforced Grades -
Page 17 and 18:
Table 6: Glass-Reinforced Grades -
Page 19 and 20:
Table 8: Toughened Grades - Mechani
Page 21 and 22:
Table 10: Toughened Glass-Reinforce
Page 23 and 24:
Table 12: Toughened Glass-Reinforce
Page 25 and 26:
Table 14: Mineral and Mineral/Glass
Page 27 and 28: Mechanical Properties The mechanica
Page 29 and 30: Figure 10: Tensile Elongation of 30
Page 31 and 32: Tensile Modulus, GPa Figure 18: Ten
Page 33 and 34: Figure 23: Flex Strength of GR A-10
Page 35 and 36: Compressive Strength and Modulus Co
Page 37 and 38: Figure 33: Izod Impact of Amodel ET
Page 39 and 40: Table 18: Poisson’s Ratio for Amo
Page 41 and 42: Figure 38: Apparent Modulus at 23°
Page 43 and 44: Stress, MPa Apparent Modulus, GPa F
Page 45 and 46: Figure 50: Flex Fatigue of GR Resin
Page 47 and 48: This phenomenon becomes of signific
Page 49 and 50: Figure 56: Dimensional Change of 40
Page 51 and 52: Figure 59: HDT of 30% - 33% GR Resi
Page 53 and 54: Table 20: Thermal Conductivity of A
Page 55 and 56: Thermal Stability The general term,
Page 57 and 58: Table 21: Relative Thermal Indices
Page 59 and 60: Table 24: Smoke Density Grade D s @
Page 61 and 62: Electrical Properties Many applicat
Page 63 and 64: Table 31: Dissipation Factor of Amo
Page 65 and 66: UL 746A Properties of Amodel Resins
Page 67 and 68: Table 40: Screening Chemical Resist
Page 69 and 70: Table 42: Screening Chemical Resist
Page 71 and 72: Design Information In this section,
Page 73 and 74: Table 46: Maximum Stress and Deflec
Page 75 and 76: Using Classical Stress/ Strain Equa
Page 77: Figure 68: Adding Ribs to Increase
Page 81 and 82: Designing for Assembly Interference
Page 83 and 84: Figure 76: Torque Developed During
Page 85 and 86: Table 48: Strain Recommendations fo
Page 87 and 88: Figure 84: Draft - Recommended Rib
Page 89 and 90: Secondary Operations Welding Compon
Page 91 and 92: Figure 91: Typical Energy-Directing
Page 93: Table 51: Suppliers of InkJet Print
Page 96: M Mechanical Design . . . . . . . .
show all

Design Guide - Solvay Plastics

Create successful ePaper yourself

Delete template?

Save as template?