force modify direct force_vector

The FORCE_VECTOR corresponds to the Adams VFORCE statement.

The FORCE_VECTOR creates an Adams translational vector force element that applies the forces between two parts of the system. The element applies an action force to the part that contains the I marker and a corresponding reaction force to the part to which the a "floating" J marker belongs. This "floating marker" is automatically created by Adams View and is positioned to be coincident with the I marker. Subsequently, the FORCE_VECTOR establishes the position of the "floating" J marker. As the system moves, Adams moves the "floating" J marker on its part to keep the "floating" J and I markers superimposed. Thus, Adams applies the reaction force to the "floating" J markers part at the instantaneous position of the I marker.

The total vector force that Adams supplies is the vector sum of the individual force components that the user specifies. The magnitude of the total vector force is the square root of the sum of the components squared. Its value will be the resultant (i.e., the square root of the sum of the squares) of the three mutually-orthogonal force components.

If the force vector is not visible on the screen, you must type the name. You may also find it convenient to type the name even if the force vector is displayed.

If you created the force vector by reading an Adams data set or graphics file, the force vector name is the letters VFO followed by the Adams data set force vector ID number. The name of Adams VFORCE/101 is VFO101, for example. If you created the force vector during preprocessing, you gave it a name at that time.

If a force vector is available by default, you may identify it by entering its name only. If it is not, you must enter its full name. To identify a force vector under another model, for instance, you may need to enter the model name as well. For example, you may specify force vector 'spring' from the model 'suspension' by entering ".suspension.spring". If you type a "?", Adams View will list the force vector available by default.

You must separate multiple force vector names by commas.

If the force vector is visible in one of your views, you may identify it by picking on any of the graphics associated with it.

You need not separate multiple force vector picks by commas.

By enclosing the name in double quotes, you may use other printable characters, or start the name with a numeral. If a name contains characters, or starts with a numeral, you must always quote the name when entering it.

Note that you can specify the parentage of an entity (e.g. what part "owns" a marker or a geometry element) when you CREATE it by changing the name. If you enter just the entity name, then the default parent will be assigned by Adams View. If you type in the full name, then you may over ride the default parent. In most cases, when creating an entity, Adams View will provide a default name. The default name that Adams View provides will specify the parentage that it has assumed. You may, or course, delete this name and use your own. The form of a full name is:

The number of levels used varies from case to case and the parentage must exist before an entity can be assigned to it.

You may also enter zero as an identifier, either explicitly or by default. The next time you write an Adams file, Adams View will replace the zero with a unique, internally-generated identifier. Adams View will permanently store this identifier with the element just as if you had entered it yourself.

Normally, you would let all identifiers default to zero, and Adams View would generate the identifiers for you. You are never required to enter a non-zero identifier. You only need to specify it if, for some reason, you wish to control the Adams file output.

The "floating" marker is automatically created by Adams View on the part specified in the J_PART_NAME parameter.

The easiest way to enter a function expression in Adams View is to use the text editor in combination with the function builder. To invoke the text editor for entering a function expression, highlight the function field and then either pick the "EDIT" button at the top of the panel or type a ^t (control-t). The Adams View "function builder" is discussed below.

The syntactical correctness of a function expression can be investigated by using the "VERIFY" button at the upper right of the text editor. If there is a syntax error, a message is printed and the cursor is put near the problem. Proper unit consistency is not checked during function expression verification.

The remainder of this explanation will cover the components of FUNCTION expressions as summarized in the following table.

FUNCTION expressions can include integers, real numbers, and exponents. In other words, any numbers that are legal in Adams are legal in a FUNCTION expression.

In a FUNCTION expression, Adams allows any of the operators **, *, /, +, and -. Adams executes these operators according to the following precedence rules:

Adams subtracts TIME from one before it performs multiplication and division.

You can include the following system constants in a FUNCTION expression:

The following example of a FUNCTION with a system constant multiplies the system constant PI by the displacement of marker 10 with respect to marker 14:

A FUNCTION expression can contain any number of blank spaces. Five consecutive blank spaces in an expression do not terminate input of the expression (by indicating that what follows is a comment) as they do in an Adams statement. However, you should remember these two restrictions.

You cannot put a blank space in the middle of a number.

Adams does not accept a blank space between a function and its left bracket. (This is true for both, FORTRAN-77 functions and Adams functions.)

You can use a comma to continue FUNCTION expressions. You can break the expression anywhere except in the middle of a number, in the middle of a name, or between a function and its left bracket. Put a continuation comma in column one of the following line before the rest of the expression. If you break the expression at a comma that is part of the expression, you must use both, the expression comma and the continuation comma. You may use more than one continuation comma to extend an expression over several lines.

The FUNCTIONS button at the right side of the Adams View text editor provides a means for constructing an Adams function string. These functions are briefly described below. Upon picking the FUNCTIONS button, you will be presented with the list of available functions in the "selection window". After you select the desired function, a panel will appear with fields representing the various parameters for the function. You will have full access to on-line help with this panel just like you have with regular panels. After you have completed the panel and selected the DONE button on the panel, the function string will be constructed and inserted at the current text cursor location in the text edit window.

A FUNCTION expression may access the current value of a system variable and use the value in computations. These values are accessed through a collection of functions. The accessible system variables include the following: Time, Mode, Displacements (Translational and Rotational), Velocities (Translational and Rotational), Accelerations (Translational and Rotational), Forces (Translational and Rotational), and User-defined variables. Invoke the text edit window and pick the FUNCTIONS button to get a list of functions that can be accessed.

In general, you use a function character string (such as DM, VX, or FZ) and a list of values (for example, i1, i2, and i3) to access a system variable in an expression. For example, the value i1 may be the name of the marker for which you want to measure a quantity (such as displacement, velocity, acceleration, or force), i2 is the name of the marker with respect to which you want to measure the quantity, and i3 is the name of the marker you want to use to resolve the components of the quantity. If you do not specify marker i3, Adams computes the result in the ground reference frame.

Arithmetic IFs allow you to conditionally define FUNCTION. The format for arithmetic IFs follows.

Adams evaluates expression 1. If expression 1 is less than zero, the arithmetic IF equals expression 2; if expression 1 equals zero, the arithmetic IF equals expression 3; and if expression 1 is greater than zero, the arithmetic IF equals expression 4.

A FUNCTION expression with an arithmetic IF and its four expressions is as given below:

If the radial velocity between markers 10 and 31 is less than or equal to zero, the value of the FUNCTION expression is zero; but if the radial velocity between markers 10 and 31 is greater than zero, the value of the FUNCTION expression is six hundred.

In some ways, you may treat IF as a variable. For example, you can place it anywhere in the expression. In addition, you can nest arithmetic IFs nine levels deep.

You can use the FORTRAN functions ABS, ATAN, ATAN2, COS, EXP, LOG, LOG10, MIN, MAX, SIN, SQRT, and TAN in your expression. For more information about these functions, see a FORTRAN reference manual. Invoke the text edit window and pick the FUNCTIONS button to get a list of functions that can be accessed.

In general, an Adams function evaluates a mathematical equation and returns a value to your FUNCTION expression. The following table lists all the Adams functions and their purposes. Invoke the text edit window and pick the FUNCTIONS button to make a list of functions that can be accessed.