Generative design shape optimization with damage prevention over loading cycles for computer aided design and manufacturing

Abstract

Methods, systems, and apparatus, including medium-encoded computer program products, for computer aided design of physical structures using generative design processes. A method includes obtaining a design space for a modeled object, one or more design criteria, one or more in-use load cases, and one or more specifications of material, wherein the design criteria comprise a required number of loading cycles for the modeled object; iteratively modifying a generatively designed three dimensional shape of the modeled object, comprising: performing numerical simulation of the modeled object, finding a maximized stress or strain element for each of the one or more in-use load cases, determining an expected number of loading cycles for each of the one or more in-use load cases, redefining a fatigue safety factor inequality constraint for the modeled object, computing shape change velocities in accordance with at least the fatigue safety factor inequality constraint, and updating the level-set representation.

1 - 23 . (canceled) 
     
     
         24 . A method comprising:
 obtaining, by a computer program, one or more load cases and one or more design criteria for a modeled object, wherein the one or more design criteria comprise a required number of loading cycles for the modeled object;   iteratively modifying, by the computer program, a three dimensional shape of the modeled object in accordance with the one or more design criteria and the one or more load cases, wherein the iteratively modifying comprises enforcing a fatigue safety factor constraint based on a comparison of the required number of loading cycles for the modeled object with an expected number of loading cycles, and the expected number of loading cycles is calculated from (i) a stress or strain value of the modeled object found in a current numerical assessment of a physical response of the modeled object, and (ii) data relating fatigue strength to loading cycles for one or more materials; and   providing, by the computer program, the three dimensional shape of the modeled object for use in manufacturing a physical structure corresponding to the modeled object using one or more computer-controlled manufacturing systems.   
     
     
         25 . The method of  claim 24 , wherein the one or more materials are two or more different materials, and the method comprises defining the fatigue safety factor constraint as a minimum of values calculated respectively for each of the two or more different materials. 
     
     
         26 . The method of  claim 25 , wherein the one or more load cases comprise two or more load cases, and the method comprises calculating the values respectively for each of the two or more different materials by summing load-specific damage fractions corresponding to the two or more load cases, wherein each load-specific damage fraction comprises a number of expected loading cycles for a respective one of the two or more different materials, divided by the required number of loading cycles for the respective one of the two or more load cases. 
     
     
         27 . The method of  claim 25 , wherein the iteratively modifying comprises computing shape change velocities using a gradient determined from a shape derivative of an aggregated fatigue metric for the modeled object. 
     
     
         28 . The method of  claim 25 , wherein the data relating fatigue strength to loading cycles comprises a set of data points for each of the two or more different materials, each of the data points comprising a load cycles number and a fatigue strength value data pair, and the method comprises calculating the values respectively for each of the two or more different materials based on (i) a number of loading cycles from one or more curves fit to the set of data points in a plastic region and an elastic region of the data relating fatigue strength to loading cycles, and (ii) a highest load cycles number from the set of data points in an endurance region of the data relating fatigue strength to loading cycles. 
     
     
         29 . The method of  claim 25 , wherein the iteratively modifying comprises computing shape change velocities using an amount determined from a shape derivative formula that approximates a shape derivative of a fatigue safety factor. 
     
     
         30 . The method of  claim 29 , wherein the shape derivative formula that approximates the shape derivative of the fatigue safety factor comprises a volume fraction or a stress based inequality constraint that is modified using an importance factor, which is adjusted based on whether or not one or more other constraints were violated in a prior iteration of the iteratively modifying. 
     
     
         31 . The method of  claim 30 , comprising:
 adjusting a target value of the volume fraction or a minimum thickness based inequality constraint between an initial target value and a final target value across multiple iterations of the iteratively modifying; and   using a proportional-integral-derivative controller to stabilize changes made in the amount determined from the shape derivative formula as the target value is adjusted across the multiple iterations.   
     
     
         32 . The method of  claim 30 , comprising using a proportional-integral-derivative controller to adjust a total contribution of the amount determined from the shape derivative formula to shape change velocities used during the iteratively modifying. 
     
     
         33 . The method of  claim 24 , wherein the iteratively modifying comprises finding the stress or strain value of the modeled object by calculating a maximum stress value for each of the one or more load cases based on at least a standard deviation of a stress distribution in the current numerical assessment of the physical response of the modeled object. 
     
     
         34 . A system comprising:
 a first computer communicatively coupled with a network, the first computer comprising a first non-transitory storage medium having instructions of a computer program stored thereon; and   a second computer communicatively coupled with the network, the second computer comprising a second non-transitory storage medium having instructions of the computer program stored thereon;   wherein the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to
 obtain one or more load cases and one or more design criteria for a modeled object, wherein the one or more design criteria comprise a required number of loading cycles for the modeled object, 
 iteratively modify a three dimensional shape of the modeled object in accordance with the one or more design criteria and the one or more load cases, wherein the iterative modification comprises enforcement of a fatigue safety factor constraint based on a comparison of the required number of loading cycles for the modeled object with an expected number of loading cycles, and the expected number of loading cycles is calculated from (i) a stress or strain value of the modeled object found in a current numerical assessment of a physical response of the modeled object, and (ii) data relating fatigue strength to loading cycles for one or more materials, and 
 provide the three dimensional shape of the modeled object for use in manufacturing a physical structure corresponding to the modeled object using one or more computer-controlled manufacturing systems. 
   
     
     
         35 . The system of  claim 34 , wherein the one or more materials are two or more different materials, and the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to define the fatigue safety factor constraint as a minimum of values calculated respectively for each of the two or more different materials. 
     
     
         36 . The system of  claim 35 , wherein the one or more load cases comprise two or more load cases, and the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to calculate the values respectively for each of the two or more different materials by summing load-specific damage fractions corresponding to the two or more load cases, wherein each load-specific damage fraction comprises a number of expected loading cycles for a respective one of the two or more different materials, divided by the required number of loading cycles for the respective one of the two or more load cases. 
     
     
         37 . The system of  claim 35 , wherein the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to compute shape change velocities during the iterative modification using a gradient determined from a shape derivative of an aggregated fatigue metric for the modeled object. 
     
     
         38 . The system of  claim 35 , wherein the data relating fatigue strength to loading cycles comprises a set of data points for each of the two or more different materials, each of the data points comprising a load cycles number and a fatigue strength value data pair, and the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to calculate the values respectively for each of the two or more different materials based on (i) a number of loading cycles from one or more curves fit to the set of data points in a plastic region and an elastic region of the data relating fatigue strength to loading cycles, and (ii) a highest load cycles number from the set of data points in an endurance region of the data relating fatigue strength to loading cycles. 
     
     
         39 . The system of  claim 35 , wherein the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to compute shape change velocities during the iterative modification using an amount determined from a shape derivative formula that approximates a shape derivative of a fatigue safety factor. 
     
     
         40 . The system of  claim 39 , wherein the shape derivative formula that approximates the shape derivative of the fatigue safety factor comprises a volume fraction or a stress based inequality constraint that is modified using an importance factor, which is adjusted based on whether or not one or more other constraints were violated in a prior iteration of the iterative modification. 
     
     
         41 . The system of  claim 40 , wherein the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to
 adjust a target value of the volume fraction or a minimum thickness based inequality constraint between an initial target value and a final target value across multiple iterations of the iterative modification, and   use a proportional-integral-derivative controller to stabilize changes made in the amount determined from the shape derivative formula as the target value is adjusted across the multiple iterations.   
     
     
         42 . The system of  claim 40 , wherein the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to use a proportional-integral-derivative controller to adjust a total contribution of the amount determined from the shape derivative formula to shape change velocities used during the iterative modification. 
     
     
         43 . The system of  claim 34 , wherein the instructions of the computer program are configured to cause the first and second computers to operate cooperatively to find the stress or strain value of the modeled object, during the iterative modification, by calculating a maximum stress value for each of the one or more load cases based on at least a standard deviation of a stress distribution in the current numerical assessment of the physical response of the modeled object. 
     
     
         44 . A non-transitory computer-readable medium encoding a computer program operable to cause one or more data processing apparatus to perform operations comprising:
 obtaining one or more load cases and one or more design criteria for a modeled object, wherein the one or more design criteria comprise a required number of loading cycles for the modeled object;   iteratively modifying a three dimensional shape of the modeled object in accordance with the one or more design criteria and the one or more load cases, wherein the iteratively modifying comprises enforcing a fatigue safety factor constraint based on a comparison of the required number of loading cycles for the modeled object with an expected number of loading cycles, and the expected number of loading cycles is calculated from (i) a stress or strain value of the modeled object found in a current numerical assessment of a physical response of the modeled object, and (ii) data relating fatigue strength to loading cycles for one or more materials; and   providing the three dimensional shape of the modeled object for use in manufacturing a physical structure corresponding to the modeled object using one or more computer-controlled manufacturing systems.   
     
     
         45 . The non-transitory computer-readable medium of  claim 44 , wherein the one or more materials are two or more different materials, the operations comprise defining the fatigue safety factor constraint as a minimum of values calculated respectively for each of the two or more different materials, and the iteratively modifying comprises computing shape change velocities using a gradient determined from a shape derivative of an aggregated fatigue metric for the modeled object. 
     
     
         46 . The non-transitory computer-readable medium of  claim 44 , wherein the iteratively modifying comprises finding the stress or strain value of the modeled object by calculating a maximum stress value for each of the one or more load cases based on at least a standard deviation of a stress distribution in the current numerical assessment of the physical response of the modeled object.