Ansys培训_随机振动分析
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1. 2. –
•
LMB to select the top Body in the Part list. Hold <shift> and LMB on the last Surface Body. Note: By highlighting “all”, we can set the thickness on the first one, and the same thickness gets assigned to all of them.
• • • 目标是研究桁架结构的振动特性. 这个练习将检查钢结构桁架由于加速度谱产生的 位移和应力. PSD谱可分为加速度、速度和位移.
Training Manual
•
The spectrum will typically be measured during physical tests or documented in a written specification relating to the system or component.
随机振动分析
定义和目的
什么是PSD? • PSD是激励和响应的方差随频率的变化。
Training Manual
– PSD曲线围成的面积是响应的方差. – PSD的单位是 方差/Hz (如加速度功率谱的单位是 G2/Hz). – PSD可以是位移、速度、加速度、力或压力.
DYNAMICS 11.0
随机振动分析
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 模态分析结束. • 可以查看模态结果，如右图所示. • 可以查看动画.
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 可以看到在谱分析中的初始条件已经 自动设置成模态分析的结果. • 设置阻尼（恒定阻尼比）0.05
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • • 选择激励方向为Y. 选择Solve. 求解结束后可以查看结果，可以选择1sigma到3sigma结果.
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • 如果列出了结果 更改阻尼比为0.05，查看结果.
Of course one or more individual bodies can be redefined to different thicknesses later if necessary.
5
5. Left click in the thickness field and set the thickness = 0.5 ”
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • • • 插入一个PSD Base Excitation. 在弹出的PSD Base Excitation详情串口，选择新的PSD载荷. 选择带G的加速度PSD，单位G^2/Hz. 设置PSD曲线
Training Manual
Training Manual
百度文库
DYNAMICS 11.0
6
Workshop – 前处理-网格尺寸
• • The assembly consists of multiple slender bodies plus a large flat Roof plate. We want to specify a relatively fine mesh size on the slender members but a larger element up top.
打开, Tower.dsdb.
Training Manual
• Browse to file if not in list
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 打开分析向导…
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 利用分析向导可以简单 地建立分析流程.可以看 到运行随机振动分析之 前需要进行模态分析.
DYNAMICS 11.0
•
Once in Simulation click on >Geometry>From File… to browse for and open girder.agdb
Workshop – 设置
1. When the Geometry has loaded, choose “Random Vibration” from the Map of Analysis Types
定义和目的
输入:
– 结构的自然频率和阵型 – 功率谱密度曲线
Training Manual
DYNAMICS 11.0
输出:
– 1s位移和应力 （用于疲劳分析）.
随机振动分析
Workbench随机振动功能
• 载荷:
– 单点激励
Training Manual
• 得到结果:
– 相对或绝对的1s 输出 – 整体结构的结果，可以进行云图显示. – 1s位移, 速度或加速度
• • The Girder has fixed constraints along all lower edges. The boundary conditions will be applied to edges.
Training Manual
DYNAMICS 11.0
Workshop – 起始页
• From the WorkBench Project Launcher start Simulation.
–
•
Training Manual
if already in Simulation use
>File>New
“No: do not save any items”
For training purposes, choose
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • 点击OK可以看到如图所示信息 当提示“Specify Number of Modes” ，输入12
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 下一步是插入约束，插入fixed support.
– 基于概率的谱分析. – 典型应用如火箭发射时结构承受的载荷谱，每次发射 的谱不同，但统计规律相同.
DYNAMICS 11.0
Reference: Random vibrations in mechanical systems by Crandall & Mark
随机振动分析
定义和目的
Training Manual
1. Note, the map will automatically highlight “Modal” too since modal is a precursor to Random Vibration simulation.
Training Manual
2. Click OK, thus accepting the default number of modes
7 8,9
DYNAMICS 11.0
7. • 8.
Change to Body Select. On the Outline Tree, RMB on the Mesh object >Insert>Sizing (for slender bodies)
1. 2. 3.
4.
In Details, Replace “Default” size with 2 (inches) RMB in Graphics Window, >Select All But then hold <CTRL> and LMB single select on the “roof body” to unselect that part from this Size object. >Apply
Training Manual
欢迎进入 ANSYS技培训第五天
Training Manual
随机振动(PSD) 分析
主要内容
• 定义和目的 • Workbench随机振动分析功能 • 分析流程
Training Manual
DYNAMICS 11.0
随机振动分析
定义和目的
什么是随机振动分析
Training Manual
– In the Details pane, notice that the “Thickness” field are displayed in yellow to indicate they are undefined.
Training Manual
4
DYNAMICS 11.0
4. Select all the bodies to assign a uniform thickness
3. Choose the U.S. inch pound unit system.
– “Units > U.S. Customary (in, lbm, lbf, …)”
DYNAMICS 11.0
1 2 3
Workshop – 前处理-壳体厚度
• • • The Girder geometry consists of surface bodies (for shell meshing) The first preprocessing task is to specify the thickness of all the surfaces. Click to fully expand the Girder “Geometry” branch.
• 和确定性谱分析不同，随机振动不能用瞬态动 力学分析代替. • 应用基于概率的功率谱密度分析，分析载荷作 用过程中的统计规律
DYNAMICS 11.0
Image from “Random Vibrations Theory and Practice” by Wirsching, Paez and Ortiz.
– The data points can be entered for each Freq & Amplitude, or a function can be entered.
DYNAMICS 11.0
A2
A3
Acceleration
A1 A4
F1
F2
F3
F4
Frequency
Workshop – 假定
DYNAMICS 11.0
• 后处理:
– 1s 可以进行云图显示.
随机振动分析
随机振动分析流程
• Model: 输电铁架 • Analysis: 地面激励PSD 分析. • Steps: 进行模态和随机 振动分析，并显示结果.
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
– By assigning larger elements on the large roof, we preserve CPU time and are able to use finer (usually more accurate) elements elsewhere.
Training Manual
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 按阻尼比0.05重新计算.
Training Manual
DYNAMICS 11.0
练习
Training Manual
• 查看如图所示桁架结构在加速度PSD激励下的响 应
DYNAMICS 11.0
Workshop – 目标
Workshop – 前处理-接触
• The assembly to be shell meshed consists of multiple surface bodies separated by small offsets that account for the physical spacing between the neutral (axis) planes of each piece of steel. • We need to use “Bonded” Contact in order to simulate the effect of welded and/or bolted assembly connectivity. 6. Click on >Connections>Create Automatic Contact • The Default definition is “Bonded”
•
LMB to select the top Body in the Part list. Hold <shift> and LMB on the last Surface Body. Note: By highlighting “all”, we can set the thickness on the first one, and the same thickness gets assigned to all of them.
• • • 目标是研究桁架结构的振动特性. 这个练习将检查钢结构桁架由于加速度谱产生的 位移和应力. PSD谱可分为加速度、速度和位移.
Training Manual
•
The spectrum will typically be measured during physical tests or documented in a written specification relating to the system or component.
随机振动分析
定义和目的
什么是PSD? • PSD是激励和响应的方差随频率的变化。
Training Manual
– PSD曲线围成的面积是响应的方差. – PSD的单位是 方差/Hz (如加速度功率谱的单位是 G2/Hz). – PSD可以是位移、速度、加速度、力或压力.
DYNAMICS 11.0
随机振动分析
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 模态分析结束. • 可以查看模态结果，如右图所示. • 可以查看动画.
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 可以看到在谱分析中的初始条件已经 自动设置成模态分析的结果. • 设置阻尼（恒定阻尼比）0.05
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • • 选择激励方向为Y. 选择Solve. 求解结束后可以查看结果，可以选择1sigma到3sigma结果.
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • 如果列出了结果 更改阻尼比为0.05，查看结果.
Of course one or more individual bodies can be redefined to different thicknesses later if necessary.
5
5. Left click in the thickness field and set the thickness = 0.5 ”
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • • • 插入一个PSD Base Excitation. 在弹出的PSD Base Excitation详情串口，选择新的PSD载荷. 选择带G的加速度PSD，单位G^2/Hz. 设置PSD曲线
Training Manual
Training Manual
百度文库
DYNAMICS 11.0
6
Workshop – 前处理-网格尺寸
• • The assembly consists of multiple slender bodies plus a large flat Roof plate. We want to specify a relatively fine mesh size on the slender members but a larger element up top.
打开, Tower.dsdb.
Training Manual
• Browse to file if not in list
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 打开分析向导…
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 利用分析向导可以简单 地建立分析流程.可以看 到运行随机振动分析之 前需要进行模态分析.
DYNAMICS 11.0
•
Once in Simulation click on >Geometry>From File… to browse for and open girder.agdb
Workshop – 设置
1. When the Geometry has loaded, choose “Random Vibration” from the Map of Analysis Types
定义和目的
输入:
– 结构的自然频率和阵型 – 功率谱密度曲线
Training Manual
DYNAMICS 11.0
输出:
– 1s位移和应力 （用于疲劳分析）.
随机振动分析
Workbench随机振动功能
• 载荷:
– 单点激励
Training Manual
• 得到结果:
– 相对或绝对的1s 输出 – 整体结构的结果，可以进行云图显示. – 1s位移, 速度或加速度
• • The Girder has fixed constraints along all lower edges. The boundary conditions will be applied to edges.
Training Manual
DYNAMICS 11.0
Workshop – 起始页
• From the WorkBench Project Launcher start Simulation.
–
•
Training Manual
if already in Simulation use
>File>New
“No: do not save any items”
For training purposes, choose
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• • 点击OK可以看到如图所示信息 当提示“Specify Number of Modes” ，输入12
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 下一步是插入约束，插入fixed support.
– 基于概率的谱分析. – 典型应用如火箭发射时结构承受的载荷谱，每次发射 的谱不同，但统计规律相同.
DYNAMICS 11.0
Reference: Random vibrations in mechanical systems by Crandall & Mark
随机振动分析
定义和目的
Training Manual
1. Note, the map will automatically highlight “Modal” too since modal is a precursor to Random Vibration simulation.
Training Manual
2. Click OK, thus accepting the default number of modes
7 8,9
DYNAMICS 11.0
7. • 8.
Change to Body Select. On the Outline Tree, RMB on the Mesh object >Insert>Sizing (for slender bodies)
1. 2. 3.
4.
In Details, Replace “Default” size with 2 (inches) RMB in Graphics Window, >Select All But then hold <CTRL> and LMB single select on the “roof body” to unselect that part from this Size object. >Apply
Training Manual
欢迎进入 ANSYS技培训第五天
Training Manual
随机振动(PSD) 分析
主要内容
• 定义和目的 • Workbench随机振动分析功能 • 分析流程
Training Manual
DYNAMICS 11.0
随机振动分析
定义和目的
什么是随机振动分析
Training Manual
– In the Details pane, notice that the “Thickness” field are displayed in yellow to indicate they are undefined.
Training Manual
4
DYNAMICS 11.0
4. Select all the bodies to assign a uniform thickness
3. Choose the U.S. inch pound unit system.
– “Units > U.S. Customary (in, lbm, lbf, …)”
DYNAMICS 11.0
1 2 3
Workshop – 前处理-壳体厚度
• • • The Girder geometry consists of surface bodies (for shell meshing) The first preprocessing task is to specify the thickness of all the surfaces. Click to fully expand the Girder “Geometry” branch.
• 和确定性谱分析不同，随机振动不能用瞬态动 力学分析代替. • 应用基于概率的功率谱密度分析，分析载荷作 用过程中的统计规律
DYNAMICS 11.0
Image from “Random Vibrations Theory and Practice” by Wirsching, Paez and Ortiz.
– The data points can be entered for each Freq & Amplitude, or a function can be entered.
DYNAMICS 11.0
A2
A3
Acceleration
A1 A4
F1
F2
F3
F4
Frequency
Workshop – 假定
DYNAMICS 11.0
• 后处理:
– 1s 可以进行云图显示.
随机振动分析
随机振动分析流程
• Model: 输电铁架 • Analysis: 地面激励PSD 分析. • Steps: 进行模态和随机 振动分析，并显示结果.
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
– By assigning larger elements on the large roof, we preserve CPU time and are able to use finer (usually more accurate) elements elsewhere.
Training Manual
Training Manual
DYNAMICS 11.0
随机振动分析
随机振动分析流程
• 按阻尼比0.05重新计算.
Training Manual
DYNAMICS 11.0
练习
Training Manual
• 查看如图所示桁架结构在加速度PSD激励下的响 应
DYNAMICS 11.0
Workshop – 目标
Workshop – 前处理-接触
• The assembly to be shell meshed consists of multiple surface bodies separated by small offsets that account for the physical spacing between the neutral (axis) planes of each piece of steel. • We need to use “Bonded” Contact in order to simulate the effect of welded and/or bolted assembly connectivity. 6. Click on >Connections>Create Automatic Contact • The Default definition is “Bonded”