Susan M. Ward

Modeling paint and adhesive cure in automotive applications

Abstract In the development of thermoset coating and adhesive formulations, optimum cure conditions are defined based on measurements of physical properties, chemical resistance, and durability. The range of cure conditions over which a thermoset material exhibits acceptable performance constitutes a cure window for the material, and can be used to define acceptable limits of variability for production processes. There is variability intrinsic to the stoving of complex articles of manufacture: local variations in heat transfer and thermal mass result in substantial variations in temperature history. By applying chemical understanding of crosslinking processes and basic chemical engineering principles, cure strategies can be evaluated using a combination of heat transfer and chemical kinetic models. Examples drawn from research on automotive paints and adhesives are given.

Modeling foam damping materials in automotive structures

Foam damping materials judiciously placed in automotive structures efficiently reduce the vibration amplitudes of large, relatively flat exterior body panels such as the hood, roof, deck lid (trunk) and door skin. These polymer foams (typically epoxy or vinyl) have mechanical properties that depend on the foam homogeneity, degree of expansion, temperature and frequency of excitation. Standard methods for determining true bulk mechanical properties, such as Youngs modulus, shear modulus and damping terms, are discussed along with methods for determining engineering estimates of the properties as used in automotive applications. Characterizing these foam damping materials in a component or full body finite element structural model as discrete springs and dashpots provides an accurate and economical means to include these features. Example analyses of the free vibrations and forced response of a hood are presented accompanied by test data that demonstrate the accuracy of the structural model. A parametric study investigates the effect of foam material stiffness and damping properties on hood vibration amplitudes under dynamic air loading. A methodology is discussed to reduce the hood vibration level under cross-wind conditions to an acceptable level with the use of foam materials.

Service Life Heat Exposure Effects and ALuminm Aluminum Extrusion Crash Properties Relationship Under Static Axial Loading

Relationship between service life heat exposure and extruded aluminum structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum alloy extrusions each of which is subjected to two heat treatments. The aluminum extrusion investigated are 6063T6, 6061T6, 6260T6, 6014T6, and 7129T6. The two heat treatments are 177°C for 30 minutes and 200°C for 24 hours. The 200°C/24 hours treatment represents the most severe thermal exposure i.e. components adjacent to exhaust pipes and manifolds. The 200°C heat treatment is in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. These ten crash members were subjected to static axial crushing at a speed of 25.4 mm/minute (1 in/min). Force-time data was collected and responses were plotted for all tests. Force-displacement responses were integrated for the crush energy management and mean axial crush load for each of the aluminum extruded crash members. Bar charts were then generated to describe the crush loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Severe service life simulated heat exposure was found to affect the mean crush load and crush energy management of the aluminum structural crush members. The heat exposure effects on the crashworthiness of the extruded aluminum members ranged from a reduction of 8% to over 20% in the mean crush load and crush energy management with highest variation observed with the 6260T6 aluminum extrusion.Copyright

Service Life Aging and Heat Exposure Effects on Aluminum Sheet Alloy Properties and Structural Crashworthiness Under Dynamic Axial Loading

An investigation of the service life aging and heat exposure effects on sheet aluminum alloy properties and structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum sheet alloys each of which is subjected to four heat treatments. The aluminum sheet alloys investigated are 6111T4PD, 5754-O, 5182-O, 6022T4E29, and 6022T4. The four heat treatments are 177°C for 30 minutes, 200°C for 15 minutes, 200°C for 2 hours, and 200°C for 24 hours. The 200°C/24 hours treatment simulates the most severe thermal exposure i.e. components adjacent to exhaust pipes and manifolds. All 200°C heat treatments are in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. Aluminum rails of hexagonal cross-section were formed for the twenty combinations of aluminum sheet alloys and heat exposures. These twenty formed aluminum rails were then bonded and riveted using Betamate 4601 adhesive and Henrob K50742 self-piercing rivets. Once assembled, these twenty rails were subjected to dynamic axial crushing at a speed of 40 kph (25 mph). Force-Time data was collected and responses were plotted for all tests. Force-Displacement responses were then integrated for the crush energy management and mean axial crush load for each of the aluminum sheet rails. Bar charts were generated to describe the crash loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Service life simulated heat exposure was found to affect the mean crash load and crash energy management of the aluminum structural crash members. The heat exposure effects on the crashworthiness of the sheet aluminum members ranged from a reduction of [−21.6%] to an increase of [+6.8%] in the mean crash load and crash energy management with higher variation observed in the “T4” tempered aluminum alloys.Copyright

Crashworthiness of Aluminum Extrusion Under Simulated Service Life Heat Exposure

An investigation of the service life aging and heat exposure effects on extruded aluminum alloy properties and structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum alloy extrusions each of which is subjected to two heat treatments. The aluminum extrusion investigated are 6063T6, 6061T6, 6260T6, 6014T6, and 7129T6. The two heat treatments are 177°C for 30 minutes and 200°C for 24 hours. The 200°C/24 hours treatment represents an upper limit thermal exposure i.e. components adjacent to exhaust pipes and manifolds. The 200°C heat treatment was applied in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. These ten crash members were subjected to dynamic axial crashing at a target speed of 40 kph (25 mph). Force-time data was collected and responses were plotted for all tests. Force-displacement responses were then integrated for the crash energy management and mean axial crash load for each of the aluminum extruded crash members. Bar charts were then generated to describe the crash loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Service life simulated heat exposure was found to effect the mean crash load and crash energy management of the aluminum structural crash members. The heat exposure effects on the crashworthiness of the extruded aluminum members ranged from a reduction of 10% to over 20% in the mean crash load and crash energy management with highest variation observed with the 6260T6 aluminum extrusion.Copyright